The present invention relates to a device for performing spot-facings, in particular at non-accessible ends of through-holes and the like.
As is known, in mechanical technology the need often arises to perform spot-facings at the ends of holes, in order to provide, e.g., a resting seat for the head of screw elements and the like. Such spot-facings, composed of a shallow circular recess with a flat bottom, are generally executed by means of specific tools, made to rotate by the machine tool and fitted with a radial cutting edge.
When spot-facing is required at the outlet of a through hole, there is the problem of avoiding the need to remove the part being machined, in particular in the case of automatic machines, where it would be necessary to interrupt the working cycle. In order to perform spot-facing in such non-accessible regions, devices are commonly used which are provided with a tool removably mounted at the end of a stem which is suitable for being introduced through the hole of the part being machined. This solution, however, is quite disadvantageous, since it requires the removal and subsequent refitting of the tool on the device at each machining process.
In order to avoid this disadvantage, decives have been used which are provided with a tool which can be rotated in a longitudinal position with respect to the stem or pushed elastically inside the same, so as to be able to pass through the hole without having to be removed. In other words, in order to insert the stem of the device into the hole, the retraction of the tool is caused and the same is taken back into a working position after it leaves the same hole; at this point the stem is moved in the reverse direction so as to place the cutting edge in contact with the part and perform the spot-facing.
This solution, though it has many advantages, is not, however, entirely satisfactory. Indeed, the various operating steps require not-negligible times to perform the machining, as well as suitable controls on the part of the machine. Furthermore, the possibility of adjusting the size of the spot-facing to be performed is generally severely limited, so that it is necessary to provide several devices to meet all the various requirements.